6. Chemical Reactions and Energetics Flashcards
What are 5 factors that can be changed to alter the rate of a chemical reaction? [5]
Temperature / concentration of solutions / pressure of gases / surface area of solids / catalyst
What two things are needed for a chemical reaction to happen (in terms of particles? [2]
Particles need to collide / particles need to have enough energy
Describe two main ways that the rate of reaction can be measured for a reaction that produces a gas [2]
Volume of gas produced / loss of mass
Explain the effect of increasing the temperature on the rate of reaction [4]
Rate of reaction increases… particles have more kinetic energy… more frequent collisions… more successful collisions
Explain the effect of increasing the concentration / pressure on the rate of reaction [3]
Rate of reaction increases… more particles per unit volume…more frequent collisions
Explain the effect of increasing the surface area on the rate of reaction [3]
Rate of reaction increases… more particles exposed to react… more frequent collisions
What is a catalyst? [2]
A substance that speeds up the rate of a reaction but is unchanged at the end of the reaction
Explain the effect of a catalyst on the rate of reaction [4]
Rate of reaction increases… provides an alternative reaction pathway… with lower activation energy… more particles have enough energy to react
What is an exothermic reaction? [2]
A reaction that transfers thermal energy to the surroundings leading to an increase in temperature
What is an endothermic reaction? [2]
A reaction that absorbs thermal energy from the surroundings leading to a decrease in temperature
What is enthalpy change? [1]
The difference between the energy required to break bonds and the energy given out when bonds are made
Explain an exothermic reaction in terms of bond breaking and bond making [2]
Less energy is absorbed to break bonds and more energy is released when bonds are made
Explain an endothermic reaction in terms of bond breaking and bond making [2]
More energy is absorbed to break bonds and less energy is released when bonds are made
What is activation energy? [1]
The minimum energy colliding particles need to have in order to react
